David Hall was among several workers at the Bathurst plant of Downer EDI who allegedly subjected teenage apprentice Alec Meikle to relentless bullying after he joined the company in January 2008 at the age of 16.

Ten months later, after a battle with depression and anxiety that psychiatrists believe was brought on by the treatment he received, Alec committed suicide.

On Monday, Mr Hall told the continuing inquest into Alec's death he had sprayed the teenager with contact cleaner as he welded a metal plate, knowing the solution would probably flare up.

The teenagers glove and forearm briefly caught alight, singeing his arm hairs.

''What made you decide to do that to Alec?'' counsel assisting the inquest Steven Kelly asked.

''Just loss of concentration I guess - loss of thought, ''Mr Hall replied.

Mr Hall, who is now in his 11th year at Downer, said those in the area had a laugh and conceded what happened would have been traumatic for Alec.

''I know how it looks but I didn't think he was being singled out,'' he said.

Mr Hall also confessed to having a central role in the creation of the so-called ''sphincter dilation chart'' upon which Alec's work mistakes were recorded.

He admitted that Alec was made aware of a threat that if he reached the top of the chart he would be sexually assaulted with a metal dildo.

''It was just a joke, it was not as if we were actually going to do that,'' he said.

''Looking back now, it was a stupid thing to do,'' Mr Hall said, adding that at the time it was a joke among three or four of them, Alec included.

After initially telling the inquest the purpose of the chart was to ''encourage'' Alec to improve, Mr Hall conceded it had the opposite effect.

But he said that if the youngster had complained about the chart, they would have taken it down. ''If he had ever said it was offensive, it would have been gone,'' he said.

He described Alec's death as ''a tragedy''. ''I didn't sort of see it coming,'' he said.

Earlier, the inquest heard that Mr Hall and a colleague involved in the creation of the chart, Ben Eagle, had been victims of what they described as ''practical jokes '' early in their careers.

These included being dragged across the shop floor by the feet, being water bombed, hit with balls covered in electrical tape and having the gas turned down or off while welding.

''It's just the way it was I guess - it's an old industry that hasn't sort of changed,'' Mr Hall said.

The inquest continues.